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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 Feb 2007 16:42:08 IST
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MULTIPLE ANSWER QUESTION AN IDEAL MONOATOMIC GAS AT NTP IS ENCLOSED IN AN ADIABATIC VERTICAL CYLINDER BETWEEN TWO LIGHT MOVABLE PISTONS (ONE UP AND ONE DOWN). SPRING WITH FORCE CONSTANT K IS CONNECTED TO THE UPPER PISTON AND IS IN A RELAXED STATE INITIALLY. THE LOWER PISTON IS MOVED UP BY A DISTANCE OF H/2, H BEING THE INITIAL LENGTH OF GAS COLUMN. IT IS OBSERED THAT THE UPPER PISTON MOVES UP BY H/16. Q. WHEN THE LOWER PISTON IS MOVED UPWARDS BY H/2,THE COMPRESSION A) LEADS TO COOLING B) TAKES PLACE ISOTHERMALLY C) TAKES PLACE ADIABATICALLY D) LEADS TO HEATING
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22 Feb 2007 17:22:42 IST
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experts pleez help
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22 Feb 2007 19:17:56 IST
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zzzzzzzzzzzzzzzzzzz wake me up when september ends...
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Since Cylinder is adiabatic, hence this process is adiabatic. P1,V1 initial volume and initial pressure P2, V2 final pressure and volume V1=HA , where A is cross-sectional Area V2=A(H/2 +H/16)=9HA/16 P1/P2=(V2/V1) Work done during the process: W=(P1V1-P2V2)/(-1)=(P1V1)[1-(V1/V2) ]/(-1)= -0.7013P1HA where =5/3 Since it is negative, which means work is done upon the gas, hence temperature will rise. Process is adiabatic. Observe if upper lead's motion were restricted, W= -0.881P1HA ( V2=HA/2 in this case). The work done in this case is higher than previous case, and the difference is being stored in the spring as potential energy.
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22 Feb 2007 19:40:29 IST
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thanks for ur answer
but one more doubt
correct me if i'm wrong
if extra energy is stored as p.e. of spring then why is there an increase in internal energy afterall
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22 Feb 2007 20:04:11 IST
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please help yahiyafirdous...or ne1 else
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22 Feb 2007 23:26:44 IST
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Hi Rik There is a compression in the system, so there is some external force which is compressing the gas. This external agent is doing work on gas. Apart of this energy increases internal energy of gas and remaining part is stored as P.E. in the spring. Sum total of these two equals the energy imparted by the external agent. I hope it may clear your doubt. If you need further explaination or think I am wrong please do cotact me.
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22 Feb 2007 23:35:24 IST
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is the answer C,D.first tell me this then i'll explain
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light travels the fastest ??? NO
wherever light goes it always finds that darkness has already got there |
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24 Feb 2007 09:42:05 IST
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yes the answer is C and D
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24 Feb 2007 09:45:53 IST
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i think i got it thanks !!
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4 Mar 2007 00:14:15 IST
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C & D are correct ans.
Enthalpy, H= PV, now as the vol has decreased the enthalpy " appears" to have decreased. But, since the scenario is diff., and we can say that the energy of the gas has to increase. this implies heating.
the process is adiabetic(obviously).
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